why do some have a full strip of red and others have a gap in the middle i dont get it????

i might be swapping my smoked jewels on here with somone but looking and theres 2 different styles of the rear jewels in the lighter colours theres one with a gap in the middle/no reflecter and theres on that goes all the way accross.
i want to swap my smoked for lighter jewels can somone help me out???#
cheers
jim

i might be swapping my smoked jewels on here with somone but looking and theres 2 different styles of the rear jewels in the lighter colours theres one with a gap in the middle/no reflecter and theres on that goes all the way accross.
cheers
jim